Infrared spectroscopy is a critical technique for analyzing the structure of organic compounds, offering a spectrum rich in absorption bands compared to UV spectroscopy. It involves the excitation of molecules to higher vibrational levels when they absorb infrared radiation, with only those transitions that change the dipole moment being observed. This technique highlights that vibrational transitions linked to certain bonds (e.g., C=O, N-H) are infrared active, while others (e.g., C-C bonds in symmetrical alkenes) are not.

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Infrared spectroscopy
Infrared spectroscopy is an inportant record which gives information
about the struture of a compound .Unlike UV. Spectroscopy which
comprises of relatively few peaks , this technique provides a spectrum
containing a large number of absorption bands from which a wealth of
information is provided about the struture of a organic compound .
Principle of the infra red Spectroscopy
The absorption of the infra red radiation causes excitation of the
molecule from the lower to the higher vibrational level.We know that
each vibrational level is associated with a number of spaced rotational
levels. Clearly the infra red spectra is considered as vibrational –
rotational spectra. All the bonds in a molecule are not capable of
absorbing infra red radiation but only those which are accompanied by a
change in dipole moment will absorb in the infra red region .Such
vibrational transitions which are accompanied by a change in dipole
moment of the molecule are called infra red active transitions. Thus
these are responsible for absorption for absorption of energy in the infra
red region .On the other hand the vibrational transitions which are not
accompanied by a change in dipole moment are not directly observed
and these are infra red inactive.Fof ,vibrational transitions of C=O,N-H,O-
Hetc bands are accompanied by a change in dipole moment and thus
absorb in the infra red region .But transitions in carbon carbon bonds i
symmetrical alkenes and alkynes are not accompanied by the change in
dipole moment and hence do not absorb in the infra red region

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